The invention relates to circuit arrangements for cable checking, cable testing, cable diagnosis and/or cable fault localization with                a voltage source having a first voltage multiplier for a positive voltage and a second voltage multiplier for a negative voltage        current sources that are connected to one another in combination with the voltage multipliers to generate a test voltage over the load impedance of the cable to charge and discharge the load capacitance of the cable and        a control device that is interconnected with the voltage source and the current sources and devices with a circuit arrangement of that type.        
A method of checking the insulation of electrical operating equipment and a circuit arrangement for carrying out the method are known from the document DE 195 13 441 A1. A circuit arrangement of that type can be used to measure the loss factor. The loss factor (tan delta) of the test specimen is determined from the phase positions of the test voltage and the test current induced from that. The loss factor is a measurement of the loss of the energy that is electrically or electromagnetically dissipated and is therefore a characteristic of the electrical properties of the test specimen. The AC voltage for the testing is generated in multiple steps from a mains voltage. A DC voltage is generated from the mains voltage with the aid of a rectifier. This is converted into AC voltages with the mains frequency or a multiple of the mains frequency, which are modulated in terms of their amplitude with AC voltages of a lower frequency. A high, amplitude-modulated voltage with a very low frequency, with which a test specimen is charged up in a defined manner via a rectifying circuit and subsequently discharged in a defined manner via a high-voltage circuit breaker, is generated via conversion of the low voltages by means of high-voltage transformers. Via a control process, the course of the high voltage measured over a voltage divider is compared in a time-critical fashion with the desired preprogrammed waveform and amplitude and adherence is guaranteed, among other ways, via intervention into the switching points in time in switching elements of H bridges. This regulatory intervention leads to corners in the progression of the test voltage, which in turn cause harmonic waves and noise. There is a negative influence on the precision of the measurement process because of that.
The document DE 10 2012 024 560 B3 involves a circuit arrangement and a method for generating a test voltage and a testing device for determining a loss factor that contains the circuit arrangement. The circuit arrangement is essentially comprised of two high-voltage sources for generating a positive and a negative high voltage with a variable amplitude and a high-voltage switch arrangement arranged between the outputs of the high-voltage sources and the test specimen for successive charging and discharging of the test specimen. Via a control process, the current test voltage is measured in the test specimen and, in dependence upon that, it influences the high-voltage switch arrangement for defined charging and discharging of the test specimen. The control process does not have an effect on the high-voltage sources. A separate control unit connected to the high-voltage sources generates an independent clock signal, so a high voltage is provided that is synchronized, predefined and not influenced by the control process. The high-voltage sources provide a high voltage of variable amplitude that is synchronized with the aid of a clock signal and precisely predefined in terms of its waveform and phase position.
The high-voltage switch arrangement is comprised of two semiconductor switch arrangements in the form of voltage-controlled current sources that are fed back via an amplifier in each case. A lead-in voltage that puts the current sources in a position to regulate the output voltage is necessary for the operation of the current sources. At the same time, efforts are taken to keep the lead-in voltage as small as possible and to consequently minimize the power dissipation. It is to be noted in this context that the output current is chiefly determined by the choice of the test voltage and the test specimen that is connected. It cannot be influenced by a suitable design of the high-voltage testing device. A lead-in voltage that is higher than that in the solution in the document DE 195 13 441 A1 is therefore required to regulate the current sources.
The document DE 10 2013 008 611 A1 involves a high-performance, high-voltage testing device; the means for generating the test voltage have at least two voltage-amplifying branches, of which a first voltage-amplifying branch serves to generate the positive half-cycles of the test voltage and a second voltage-amplifying branch serves to generate the negative voltage half-cycles of the test voltage. Furthermore, a measuring circuit exists to measure the test voltage to be applied to a test object and the test current caused by this in the test object. The testing device distinguishes itself by the fact that each voltage-amplifying branch is built into a separate assembly with integrated active air cooling.
Moreover, a circuit arrangement for a voltage amplitude of at least 100 kV as well is known from the document Kearley, S. J.; MacKinlay, R. R.: Discharge measurements in cables using a solid state 30 kV bipolar low frequency generator. In: Dielectric Materials, Measurements and Applications, 1988, Fifth International Conference on, 1988, 171-174. A test voltage that can be regulated in terms of its curve is generated via a semiconductor switch arrangement acting as a controllable current source for defined charging and discharging of a test object; the positive or negative high voltage generated by the upstream components of the voltage-amplifying branch can be transformed into positive or negative half-cycles with an evaluation of the test current and/or the test voltage measured in the test object.